Parallel cycle-based branch-and-bound method for Bayesian network learning

Pattern Analysis and Applications - Bayesian networks (BNs) are one of the most commonly used models for representing uncertainty in medical diagnosis. Learning the exact structure of a BN is a...     

Perturbed solution of free non-linear vibrations of composite beams

The aim of this study is to characterize the free non-linear vibration behavior of composite beams by using polynomial finite element method with shape functions based on Legendre polynomials or sinusoidal functions. The beams are subjected to different boundary conditions. Non-linear frequencies and modes shapes are obtained using asymptotic linearization method applied on the fundamental vibrating mode. The different composite beams are subjected to different layer dispositions. The nature of the interface between layers is of no object in this study. Navier–Bernoulli hypothesis on the transverse sections is adopted. The study concerns the influence of geometrical non-linearities of the free dynamical behavior. The analysis is performed thus by considering the influence of the vibration amplitude on the modal frequencies of the structure. The solutions are obtained by numerical simulation and by semi-analytical method using asymptotic linearization applied in the real temporal modal space. The numerical values are compared to the different ones obtained in literature.     

Modelisation du depot de paraffine lors d'un ecoulement ascendant de petrole

A study on the upslope flow of heated petroleum paraffin was conducted based on motion equations and heat transfer, which were rewritten in a completely dimensionless form to analyze the influence of temperature on the position of the deposit point and its change over time. A numerical resolution of the new equation system, based on the Runge‐Kutta 4th order method, was performed for two current practical cases to avoid the line obstruction problem.     

Numerical investigation of the partial oxidation in a two-stage downdraft gasifier

This paper presents a 2D axisymmetric CFD model of the oxidation zone in a two-stage downdraft gasifier. The purpose of this study is to investigate in detail this zone, which is crucial for tar cracking. Results fit satisfactorily to the experimental data regarding temperature pattern and tar concentration. Simulations highlighted several crucial points of the process: (a) tertiary tar are mainly destructed by combustion; (b) pyrolysis gas composition significantly influences the process; (c) the air injector design is fundamental in gasification as the air velocity and the air/fuel ratio have a great influence on the process; and (d) there is a critical injection velocity (about 34 m s⁻¹ in this case) that dramatically changes the flow pattern.     

Transient analysis of a grid connected wind driven induction generator using a real-time simulation platform

Due to its simple construction, ruggedness and low cost, the induction generator driven by a wind turbine and feeding power to the grid appears to be an attractive solution to the problem of growing energy demand in the context of environmental issues. This paper investigates the integration of such a system into the main utility using RT-Lab? (Trademark of Opal-RT Technologies) software package running on a simple off-the-shelf PC. This real-time simulation platform is now adopted by many high-tech industries as a real-time laboratory package for rapid control prototyping and for Hardware-in-the-Loop applications. Real-time digital simulation results obtained during contingencies, such as islanding and unbalanced faults are presented and analysed.     

Microstructural and Mechanical Properties of Ni-Base Thermal Spray Coatings Deposited by Flame Spraying

In this work, two different Ni-base powders, namely, ProXon 21021 (P21) and ProXon 21031 (P31), were sprayed onto a steel substrate 35CrMo4 using a thermal flame spray technique. The morphology and chemical composition of the phases that are present in the powders and coatings were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The hardness and wear resistance of the coatings were investigated. The XRD analysis revealed that the phases present in the coatings are different from the initial powders. In addition, some inhomogeneities such as oxides, porosity, and unmelted particles were observed by SEM. It was found that the P31 spray-coated exhibited higher microhardness, higher wear resistance, and significantly lower friction coefficient in comparison with those of P21 coatings.     

Numerical simulation of squat reinforced concrete wall strengthened by FRP composite material

The advanced design rules and the latest known earthquakes, have imposed a strengthening of reinforced concrete structures. Many research works and practical achievements of the application of the external reinforcement by using FRP composite materials have been particularly developed in the recent years. This type of strengthening seems promising for the seismic reinforcement of buildings. Among of the components of structures that could affect the stability of the structure in case of an earthquake is the reinforced concrete walls, which require in many cases a strengthening, especially in case where the diagonal cracks can be developed. The intent of this paper is to present a numerical simulation of squat reinforced concrete wall strengthened by FRP composite material (carbon fiber epoxy). The intent of this study is to perform finite element model to investigate the effects of such reinforcement in the squat reinforced concrete walls. Taking advantage of a commercial finite element package ABAQUS code, three-dimensional numerical simulations were performed, addressing the parameters associated with the squat reinforced concrete walls. An elasto-plastic damage model material is used for concrete, for steel, an elastic-plastic behavior is adopted, and the FRP composite is considered unidirectional and orthotropic. The obtained results in terms of displacements, stresses, damage illustrate clearly the importance of this strengthening strategy.     

Effects of embedded streamwise vorticity on turbulent mixing

This work concerns the characterization of turbulent flow underlying mixing in the presence of streamwise vorticity. An experimental test section made of a cylindrical tube equipped with seven rows of streamwise vortex generators was designed and constructed for this study. Each row is composed of four vortex generators fixed symmetrically on the tube wall. This new type of mixer, called a high-efficiency vortex (HEV) mixer, generates coherent structures in the form of longitudinal counter-rotating vortices. The resulting flow enhances radial mass transfer and thus facilitates particle dispersion and mixing. The energy cost of this mixer used as an emulsifier has been evaluated as up to a thousand times less than that of other static mixers for a given interface area generation (Lemenand et al. [1] and [2]).The aim of this work is to study experimentally and numerically the turbulence structure and mixing properties of the flow composed of streamwise vortices superimposed on a turbulent flow, in particular the more energetic structures present in the base flow. Experiments were carried out in the test section in a flow loop by measuring instantaneous velocities by laser Doppler anemometry. Numerical simulations of the velocity distribution and turbulence field inside the flow were conducted for various turbulence models using a computational fluid dynamic CFD package. Attention is focused on the evolution and distribution of turbulent kinetic energy dissipation as the underlying mechanism for turbulent mixing. Mean and turbulent quantities are compared with experimental results.Both laboratory experiments and numerical simulations show a vortex zone behind each tab that could explain the efficiency of the HEV mixer. This study provides a basis for understanding the physical mechanisms in the mixing and homogenizing of the flow and therefore the efficiency of the mixer.     

Structural Contour Map of the Iota Carbonic Anhydrase from the Diatom Thalassiosira pseudonana Using a Multiprong Approach

Carbonic anhydrases (CAs) are a family of ubiquitous enzymes that catalyze the interconversion of CO₂ and HCO₃⁻. The “iota” class (ι-CA) was first found in the marine diatom Thalassiosira pseudonana (tpι-CA) and is widespread among photosynthetic microalgae and prokaryotes. The ι-CA has a domain COG4875 (or COG4337) that can be repeated from one to several times and resembles a calcium–calmodulin protein kinase II association domain (CaMKII-AD). The crystal structure of this domain in the ι-CA from a cyanobacterium and a chlorarachniophyte has been recently determined. However, the three-dimensional organization of the four domain-containing tpι-CA is unknown. Using biophysical techniques and 3-D modeling, we show that the homotetrameric tpι-CA in solution has a flat “drone-like” shape with a core formed by the association of the first two domains of each monomer, and four protruding arms formed by domains 3 and 4. We also observe that the short linker between domains 3 and 4 in each monomer confers high flexibility, allowing for different conformations to be adopted. We propose the possible 3-D structure of a truncated tpι-CA containing fewer domain repeats using experimental data and discuss the implications of this atypical shape on the activity and metal coordination of the ι-CA.